Where are B and T cells formed?
Bone marrow
How do B and T cells clone?
Mitosis
How does HIV infect the body?
GP120 molecules on the HIV bind to the CD4 receptors on T helper cell
Viral envelope fuses with cell membrane and enters the cell
Reverse transcriptase converts the virus’ RNA into DNA
This DNA is integrated into host cell’s DNA by intergrase
This allows new viral proteins to be produced via transcription/translation
After many viral proteins have been produced, cell bursts and proteins go on to infect other T helper cells
What type of virus is HIV?
Retro virus
How do T killers cells kill cells?
Release enzymes that make holes in membrane of infected cell
This causes cell lysis
What is a lymphocyte?
White blood cell
Two types of white blood cell?
B and T cells
How do B cells fight infection?
Produce antibodies (immunoglobulins)
These bind to the antibodies and help to identify the pathogen
They also neutralise bacteria toxins
Type of receptors on T helper cells
CD4
Type of receptors on T killer cells
CD8
How do macrophages fight infection?
Digest cell
Displays cell’s antigens on its surface ;becomes an antigen presenting cell
Steps of clonal selection
Antigens bind to B cell that has correct receptor
B cell becomes an antigen presenting cell
Active T helper cell with complimentary receptor binds to the B cell and releases cytokines which stimulate B cell
B cell divides to produce B memory cells and B effector cells
B effector cells differentiate into plasma cells which produce antibodies
Explain how infection by HIV could increase the risk of a person developing a disease such as tuberculosis
- HIV affects T helper cells
- Lack of functional white blood cells mean a person is more susceptible to disease
What does AIDS stand for?
Acquired immune deficiency syndrome
What does HIV stand for?
Human immunodeficiency virus
What does the viral enzyme reverse transcriptase do?
Stimulates a cell to make viral DNA from a vital RNA template
How is HIV transmitted between people?
Name three
Body fluids
- Semen
- Blood transfusions
- Transplants
- Contaminated needles
- In mother’s milk
Why is it difficult to develop a vaccine for HIV?
- The arrangement of proteins on the outer coat of the virus keep changing
- This means there are many strains of AIDS virus around the world
- The virus is still mutating
How did the first class of anti-HIV drugs work?
- They were nucleoside reverse transcriptase inhibitors
- Block the action of reverse transcriptase enzyme
- AZT is an example of this type of drug
Why is one type of drug unlikely to be effective against HIV?
- HIV multiplies
- Most new copies produced are mutations
- Some of these mutations will be resistant to the drug
What are social factors that might inhibit the tackling of AIDS?
- Some societies reject pre-marriage sex/homosexuality
- Birth control not supported by the Catholic church
- HIV positive people may feel stigmatised and not come forward for treatment
What are biological factors that inhibit the tackling AIDS?
- HIV is slow acting with a ten year incubation period
- This means there are no signs of a person having the virus
- Multiple transmission methods
- Maternal transmission to foetus impossible to stop
What economic factors can inhibit the tackling of AIDS?
- HIV is widespread
- This means tracing everyone that is HIV positive can be difficult and expensive
What does a lysozyme do?
-Breaks down bacterial cell wall
-
Cells11
-
Biodiversity6
-
Bacteria And Viruses13
-
Natural Selection6
-
Forensic Biology5
-
Energy3
-
Climate Change2
-
Immunity28
-
Math Skills16
-
Ecosystems33
-
Photosynthesis22
-
Climate Change4
-
Muscles And Movement25
-
Aerobic And Anaerobic Respiration35
-
The Nervous System42
-
Peak Performance - Heart And Lungs99
-
Homeostasis - Breaking Out In A Sweat33
-
Exercise - Overdoing It62
-
Reception Of Stimuli - Eyes28
-
Topic 37
